Muffler with tuned silencing chambers



Oct. 19, 1965 J. C. WALKER MUFFLER WITH TUNED SILENCING CHAMBERS Filed Oct. 24, 1965 '"ELEI:

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E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E 2 Sheets-Sheet 1 INVENTOR. 1&7??? C. )4 4/'%cr Oct. 19, 1965 J. c. WALKER MUFFLER WITH TUNED SILENCING CHAMBERS 2 Sheets-Sheet 2 Filed 001;. 24, 1963 United States Patent 3,212,603 MUFFLER WITH TUNED SELENCING CHAMBERS John C. Walker, Jackson, Micln, assiguor to Walker Manufacturing Company, a corporation of Delaware Filed Oct. 24, 1963, Ser. No. 318,653 Claims. (Cl. 181-48) My invention relates to gas silencing devices and, in particular, concerns a silencing device that is useful in the exhaust systems of automotive internal combustion engines.

It is an object of my invention to provide a silencing device that may be readily manufactured, which silences more than one frequency or type of noise, and which is adapted for use in conjunction with a conventional muffler to provide better performance than a resonator type muffler.

Another object is to provide a small diameter silencer that may be used in an automotive exhaust system developed by the assignee hereof wherein a multiplicity of small size silencing components are distributed over the entire length of the system.

The invention accomplishes the foregoing and other objects by means of a simple three-part assembly of gas flow conduit, intermediate shell, and outer housing which is formed so as to provide a series of spit chambers and a quarter wave length or quincke tuning chamber.

The invention is illustrated in the accompanying drawings in which:

FIGURE 1 is a longitudinal cross section through one form of silencer embodying the invention;

FIG. 2 is a section along the line 22 of FIG. 1;

FIG. 3 is a perspective view, partly broken away, of another form of the invention;

FIG. 4 is an enlarged cross section along the line 44 of FIG. 3; and

FIG. 5 is a cross section similar to FIG. 4 of another modification.

The silencer 1 comprises a housing 3, a gas flow conduit 5 coaxial with and running through the housing, and an intermediate shell 7 which is substantially shorter in length than the housing 3 or conduit 5. The shell 7 is reduced in diameter at various sections 9, 11, 13, and to fit around and be attached to the conduit 5 as by spotwelding. The shell forms three closed chambers 17, 19, and 21 around the conduit 5 and these may be of the same or different lengths. The conduit 5 has banks 23, 25, and 27 of louvers in each chamber, respectively, and the banks may be of different sizes and numbers of louvers from chamber to chamber. It will be understood that by making the chambers of different sizes and/or the louver banks of different total areas from chamber to chamber that a wider range of frequencies may be attenuated than if the chambers are identical. The spit chambers remove relatively high frequencies and roughness in the gas.

Upstream of the shell 7, the tube 5 is provided with a bank of louvers 29 which connect the inside of the pipe 5 to the chamber 31 which runs the full length of housing 3 and on the outside of shell 7. By properly selecting the length of the chamber 31 in proper relationship to the frequency to be silenced, it may be used to act as a quincke or quarter wave tuning tube. In this case the distance from the downstream end of the bank of louvers 29 to the downstream end of chamber 31 would be one quarter of the wave length of the frequency to be silenced subject to such adjustments as may seem desirable to obtain maximum total silencing effect. For example, in one application the theoretical quarter wave length was 41 inches but the best total silencing was obtained with a length of 37 inches.

The use of flat louvers as the communication with the chamber 31 gives some anti-roughness or high frequency attenuating effect. However, it is possible to use one large or several small openings or to use other types of communication between tube 5 and chamber 31, various such forms of acoustic connection being known in the art. The bank of louvers 29 should be located as close as possible in the exhaust system to an antinode of the frequency to be silenced, preferably the first antinode.

The opposite ends of the shell 3 are swaged down to fit around the ends of the tube 5 and form inlet and outlet bushings 33 and 35 to provide a means for attachment to other components in an exhaust silencing system. If desired, however, the inner tube 5 may be extended out of one or both ends to provide the attachment bushings.

In use, gas fiow through the tube 5 will be subject to the high frequency silencing effect of the series of spit chambers 17, 19, and 21 and the lower tuned frequency silencing effect of the quincke chamber 31.

The structure illustrated is capable of substantial modification, especially with respect to the number and size of the spit chambers. As indicated previously, the bank of louvers 29 is preferred but other openings may be used. In a silencing system, one or more of these units of the same or different sizes may be employed and it will be seen that the unit 1 can be bent after it has been assembled.

Because the various chambers are annular, it is possible to flatten one side of the device 1, or a portion of one side, so as to enable it to fit in a restricted space under a car, without destroying the effectiveness of the muffler as a sound attenuator.

Referring to the modification shown in FIGS. 3 and 4, the silencing device 101 has an open-ended, oval housing 103 and an inner circular gas flow tube 105 that is substantially coextensive in length with the housing. The housing is swaged down at the inlet and outlet ends 107 and 109 into tight contact with the tube 105 to form inlet and outlet bushings for the silencer 101 whereby it may be connected in an exhaust system in the usual manner. A circular inner shell 111 is telescoped over the center tube 105 and the ends 113 and 115 thereof are swaged down into tight contact with the tube. Intermediate sections 117 along the length of shell 101 are necked down into contact with the tube 105 to divide the space between the tube and shell into a series of small chambers 119. These communicate with the inside of tube 105 through banks of louvers 121 formed in the wall of the tube and therefore act as high frequency and roughness attenuating or spit chambers. The chambers 119 may be of different sizes to vary the frequency ranges that may be attenuated. Likewise, the banks of louvers 121 in the various chambers 119 may vary in size, number, and area so as to vary the attenuation from chamber to chamber and widen the frequency range affected.

Upstream of the shell 101 the tube 105 is provided with a bank of louvers 123 which connect the inside of the pipe 105 to the chamber 125 which runs the full length of housing 103 and on the outside of shell 111. By selecting the length of the chamber 125 in proper relationship to the frequency to be silenced, it may be used to act as a quincke or quarter wave tuning tube. In this case, the distance from the downstream end of the bank of louvers 123 to the downstream end of chamber 125 would be one quarter of the wave length of the frequency to be silenced, subject to such adjustments as may seem desirable to obtain maximum silencing effect.

The use of flat louvers as the communication with the chamber 123 gives some anti-roughness or high frequency attenuating effect. It is possible to use one large or several small openings or to use other types of communication between tube 105 and chamber 125, various such forms of acoustic connection being known in the art. The bank of louvers 123 should be located as close as possible in the exhaust system to an antinode of the frequency to be silenced, preferably the first antinode.

In use, gas flow through the tube 105 will be subject to the high frequency silencing effect of the series of spit chambers 119 and the lower, tuned frequency silencing effect of the quincke chamber 125.

The structure illustrated is capable of substantial modification, especially with respect to the number and size of the spit chambers. As indicated previously, the bank of louvers 123 is preferred but other openings may be used. In a silencing system, one or more of these units of the same or different sizes may be employed and it will be seen that the unit 101 can be bent after it has been assembled.

Because the various chambers are annular, it is possible to flatten one side of the device as seen at 127 so as to enable it to fit in a restricted space under a car, without destroying the effectiveness of the mufiler as a sound attenuator.

In the embodiment of FIG. 3 the shell 111 is shown as tangent to shell 103 along one side and spaced from it on the other and as concentric with tube 105. In the embodiment of FIG. 5 the shell 111a is tangent to shell 103a on both sides and on the bottom the tube 105a is also tangent to the shell 111a. The parts may be spotwelded together at points of contact as desired. Two chambers 125a are formed in FIG. 5 and these may be tuned exactly the same or to slightly different frequencies (broad banded) by making the location of the upstream louver bank closer to the inlet on one side than on the other side.

Modifications in the structure shown may be made without departing from the spirit and scope of the invention.

It is noted that the device may be reversed end for end if desirable to accommodate the location of the antinode.

I claim:

1. A gas silencing device for silencing a predetermined relatively low frequency and at least one high frequency comprising an elongated outer housing, a gas flow conduit disposed inside of said housing and extending substantially the full length thereof, an intermediate shell in said housing extending less than the length of said gas flow conduit and defining at least one high frequency tuning chamber therebetween, said inner shell, said outer housing and said conduit defining a lower frequency tuning chamber extending substantially the full length of said outer housing, said conduit having a perforate portion at one end thereof opening into said lower frequency tuning chamber and being out of communication with said lower frequency tuning chamber for substantially the remaining length thereof for silencing said relatively low frequency by functioning as a quarter wave length tuning chamber for said lower frequency, and said conduit having perforate areas opening into said high frequency tuning chamber whereby said high frequency tuning chamber functions as a spit chamber to attenuate high frequencies and roughness.

2. The invention set forth in claim 1 wherein the housing, shell and conduit are substantially coaxial.

3. The invention set forth in claim 1 wherein said perforate portion of said conduit which opens into said lower frequency tuning chamber is at the upstream end of the conduit.

4. The invention set forth in claim 3 wherein said perforate portion comprises a bank of louvers.

5. The invention set forth in claim 4 wherein the distance from the downstream end of the bank of louvers to the remote end of the lower frequency tuning chamber is approximately one quarter the wave length of said frequency to be silenced.

6. A gas silencing device as set forth in claim 1 wherein the intermediate shell has a plurality of reduced diameter portions in engagement with the conduit to divide the high frequency tuning chamber into a plurality of chambers.

7. The invention set forth in claim 1 wherein the housing and shell are tangent along one side.

8. The invention set forth in claim 7 wherein the conduit and shell are coaxial.

9. The invention set forth in claim 1 wherein opposite sides of the shell are tangent to the housing.

10. The invention set forth in claim 9 wherein the conduit is tangent to the shell at the point of tangency of the shell and housing.

References Cited by the Examiner UNITED STATES PATENTS 1,874,326 8/32 Mason.

1,878,424 9/32 Oldberg 18l48 2,027,359 1/36 Wood et al. 18149 2,035,501 3/36 Oldberg 181-48 2,038,309 4/36 Oldberg.

2,047,442 7/36 Starkweather et al. 181--48 2,109,220 2/38 Noblitt et al 181-54 2,139,151 12/38 Dererner 18148 2,147,015 2/39 Deremer 181-35 2,191,620 2/40 Muller 18148 2,251,369 8/41 Moss 18148 2,940,538 6/60 Billey 18163 3,128,841 4/64 Ludlow et al 181-59 FOREIGN PATENTS 892,780 3/62 Great Britain.

LEO SMILOW, Primary Examiner. 

1. A GAS SILENCING DEVICE FOR SILENCING A PREDETERMINED RELATIVELY LOW FREUQUENCY AND AT LEAST ONE HIGH FREQUENCY COMPRISING AN ELONGATED OUTER HOUSING, A GAS FLOW CONDUIT DISPOSED INSIDE OF SAID HOUSING AND EXTENDING SUBSTANTIALLY THE FULL LENGTH THEREOF, AN INTERMEDIATE SHELL IN SAID HOUSING EXTENDING LESS THAN THE LENGTH OF SAID GAS FLOW CONDUIT AND DEFINING AT LEAST ONE HIGH FREQUENCY TUNING CHAMBER THEREBETWEEN, SAID INNER SHELL, SAID OUTER HOUSING AND SAID CONDUIT DEFINING A LOWER FREQUENCY TUNING CHAMBER EXTENDING SUBSTANTIALLY THE FULL LENGTH OF SAID OUTER HOUSING, SAID CONDUIT HAVING A PERFORATE PORTION AT ONE END THEREOF OPENING INTO SAID LOWER FREQUENCY TUNING CHAMBER AND BEING OUT OF COMMUNICATION WITH SAID LOWER FREQUENCY TUNING CHAMBER FOR SUBSTANTIALLY THE REMAINING LENGTH THEREOF FOR SILENCING SAID RELATIVELY LOW FREQUENCY BY FUNCTIONING AS A QUARTER WAVE LENGTH TUNING CHAMBER FOR SAID LOWER FREQUENCY, AND SAID CONDUIT HAVING PERFORATE AREAS OPENING INTO SAID HIGH FREQUENCY TUNING CHAMBER WHEREBY SID HIGH FREQUENCY TUNIGN CHAMBER FUNCTIONS AS A SPIT CHAMBER TO ATTENUATE HIGH FREQUENCIES AND ROUGHNESS. 